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The history and accuracy of the Chinese gender calendar

Have you ever heard about the Chinese gender calendar? Do people really follow it? How accurate is it?

This special calendar uses the mother’s lunar age and date of conception to calculate and predict the gender of the baby. The chart is believed to have been created for the imperial family of the Qing dynasty to help them conceive sons, for the usual reasons of carrying on the family name and for working.

The Chinese are historically extremely gender-sensitive when it comes to pregnancy, which is why around the 1600s, the Chinese birth calendar was invented. It was done by calculating the yin and yang, the five elements, the eight diagrams, and the time of the day. Especially with the Chinese being gender-conscious about their baby, they had a mixture of excitement and uncertainty before a child is born due to their previous one-child policy.

So how does this special calendar work? The calendar is composed of the x and y axes. The x-axis is the lunar month of conception from January to December and the y-axis is the lunar age of the mom that ranges from 18 to 45 years old. For instance, there is a 26-year old woman, whose lunar age is 27 and got pregnant in the lunar month of July. According to the calendar, she will give birth to a baby boy.

So exactly how accurate is this? With its long history, the Chinese gender calender’s origin is extremely vague. Therefore, Eduardo Villamor, MD, Dr.PH, a professor of epidemiology at the University of Michigan School of Public Health, put the calendar to a test in which he applied 2,840,755 births that occurred between 1973 and 2006 in Sweden. Sadly, based on his research, the calendar only has a 50% chance of being right. He even stated in his study that this calendar is no better than just tossing a coin. 

Although studies show that there is only a 50% chance of it being accurate, people still choose to follow the calendar as they believe they technically have nothing to lose if the calendar ever fails them.

Aside from the calendar, did you know there is another way for the Chinese to predict the gender of a baby? This is called the cardinal number calculation method. It takes 49 as the base, added to the lunar month of conception, subtracted to the lunar age at conception. If the result is an odd number, it should be a boy; otherwise, it is a girl. For example, a 30-year old woman, whose lunar age is 31 got pregnant in the lunar month of January. The formula would be 49+1-31=19. Since 19 is an odd number, she is estimated to conceive a baby boy.

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